In situ hybridization analysis of mRNAs for tyrosine hydroxylase, cholecystokinin, enkephalin, the D-1 and D-2 dopamine receptor subtypes, and the dopamine transporter, in brains from rats treated neonatally with cocaine, are almost completed. No difference between cocaine treatment and dietary controls has been seen in mRNA concentrations in the ventral tegmentum, substantia nigra, caudate nucleus, or nucleus accumbens, for TH, CCK, ENK, D-1, or D-2 mRNAs. Dr. de Bartolomeis has recently developed a new oligonucleotide probe for the dopamine transporter, which he has characterized for specificity, and is now quantitating in the prenatal cocaine experiment.